10GbE networks for NFS, FCoE or iSCSI storage access should be configured using Cisco Platinum Class QOS for the storage traffic.

Ethernet ports for LAN access and ethernet ports for storage access may be separate or shared. Separate ports may be desired for redundancy purposes. It is the customer's responsibility to ensure external LAN and storage access networks meet UC app latency, performance and capacity requirements.

In absence of UCS 6100/6200, normal QoS (L3 and L2 marking) can be used starting from the first upstream switch to the storage array.

If disk oversubscription or storage thin provisioning are used, note that UC apps are designed to use 100% of their allocated vDisk, either for UC features (such as Unity Connection message store or Contact Center reporting databases) or critical operations (such as spikes during upgrades, backups or statistics writes). While thin provisioning does not introduce a performance penalty, not having physical disk space available when the app needs it can have the following harmful effects

SAN/NAS Link Provisioning and High Availability

Consider the following example to determine the number of physical Fiber Channel (FC) or 10Gig Ethernet links required between your storage array (such as the EMC Clariion CX4 series or NetApp FAS 3000 Series) and SAN switch for example, Nexus or MDS Series SAN Switches), and between your SAN switch and the UCS Fabric Interconnect Switch. This example is presented to give a general idea of the design considerations involved. You should contact your storage vendor to determine the exact requirement.

Assume that the storage array has a total capacity of 28,000 Input/output Operations Per Second (IOPS). Enterprise grade SAN Storage Arrays have at least two service processors (SPs) or controllers for redundancy and load balancing. That means 14,000 IOPS per controller or service processor. With the capacity of 28,000 IOPS, and assuming a 4 KByte block size, we can calculate the throughput per storage array controller as follows:

Adding more overhead, one controller can support a throughput rate of roughly 600 Mbps. Based on this calculation, it is clear that a 4 Gbps FC interface is enough to handle the entire capacity of one Storage Array. Therefore, Cisco recommends putting four FC interfaces between the storage array and storage switch, as shown in the following image, to provide high availability.

Note:

Cisco provides storage networking and switching products that are based on industry standards and that work with storage array providers such as EMC, NetApp, and so forth. Virtualized Unified Communications is supported on any storage access and storage array products that are supported by Cisco UCS and VMware. For more details on storage networking, see http://www.cisco.com/en/US/netsol/ns747/networking_solutions_sub_program_home.html.

Best Practices for Storage Array LUNs for Unified Communications Applications

There are various ways to create partitions or Logical Unit Numbers (LUNs) in the storage array to meet the IOPS requirement for Cisco Unified Communications applications (see IO Operations Per Second (IOPS)}.

The best practices mentioned below are meant only to provide guidelines. Data Center storage administrators should carefully consider these best practices and adjust them based on their specific data center network, latency, and high availability requirements.

The storage array Hard Disk Drive (HDD) must be a Fibre Channel (FC) class HDD. These hard drives could vary in size. The current most popular HDD (spindle) sizes are:

450 GB, 15K revolutions per minute (RPM) FC HDD

300 GB, 15K RPM FC HDD

Both types of HDD provide approximately 180 IOPS. Regardless of the hard drive size used, it is important to try to balance IOPS load and disk space usage.

LUN size must be less than 2 terabytes (TB) for the virtual machine file system to recognize it. For Cisco Unified Communications virtual applications, the recommendation is to create a LUN size of between 500 GB and 1.5 TB, depending on the size of the disk and RAID group type used. Also as a best practice, select the LUN size so that the number of Unified Communications virtual machines per LUN is between 4 and 8. Do not allocate more than eight virtual machines (VMs) per LUN or datastore. The total size of all Virtual Machines (where total size = VM disk + RAM copy) must not exceed 90% of the capacity of a datastore.

LUN filesystem type must be VMFS. Raw Device Mapping (RDM) is not supported.

The following example illustrates an example of these best practices for UC:

For example, assume RAID5 (4+1) is selected for a storage array containing five 450 GB, 15K RPM drives (HDDs) in a single RAID group. This creates a total RAID5 array size of approximately 1.4 TB usable space. This is lower than the total aggregate disk drive storage space provided by the five 450 GB drives (2.25 TB). This is to be expected because some of the drive space will be used for array creation and almost an entire drive of data will be used for RAID5 striping.

Next, assume two LUNs of approximately 720 GB each are created to store Unified Communications application virtual machines. For this example, between one and three LUNs per RAID group could be created based on need. Creating more than three LUNs per RAID group would violate the previously mentioned recommendation of a LUN size of between 500 GB and 1.5 TB.

A RAID group with RAID 1+0 scheme would also be valid for this example and in fact in some cases could provide better IOPS performance and high availability when compared to a RAID 5 scheme.

The above example of storage array design should be altered based on your specific Unified Communications application IOPS requirements.

Below is a graphic of an example configuration following these best practices guidelines, note there are other designs possible.

IOPS and other Performance Requirements

This page illustrates IOPS under various conditions for Unified Communications applications. This area is under construction. Check back frequently for updates.

Storage performance must support the sum of UC VM OVA IOPS. Note that addressing IOPS requirements may require higher disk/spindle counts, which may result in excess storage capacity

IOPS utilization should be monitored for each application to ensure that the aggregate IOPS is not exceeding the capacity of the array. Prolonged buffering of IOPS against an array may result in degraded system performance and delayed reporting data availability.